Light source devices that use phosphors are known as light source devices for projectors (refer to Patent Document 1). This type of light source device includes a phosphor wheel to which a phosphor has been applied and an excitation light source that irradiates excitation light upon this phosphor wheel. The phosphor wheel emits fluorescence in response to excitation light that is irradiated from the excitation light source, and this fluorescence is used as light that illuminates a display element of the projector. In addition, because continuous irradiation by excitation light of the same position on the phosphor wheel increases the temperature, the light source device causes rotation of the phosphor wheel to change the position of irradiation on the phosphor wheel that is irradiated by the excitation light.